The problem of definition has a long history and has engaged the minds of some of the most eminent thinkers in the Western tradition, from Plato and Aristotle onwards. But it is also an everyday problem constantly confronting all who have to draft or interpret the countless texts on which modern society depends. "Definition in Theory and Practice" focuses on two areas where difficulties arise in a particularly acute form: lexicography and the law. Examining a wide range of approaches and definitional techniques, backed up by detailed analyses of dictionary entries and court cases, the authors provide a comprehensive survey of their subject. They argue that what underlies the problem of definition are conflicting assumptions about the way language functions. This in-depth study will be of interest to academics researching lexicography, semantics and jurisprudence.